// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_RASTER_SINGLE_THREAD_TASK_GRAPH_RUNNER_H_
#define CC_RASTER_SINGLE_THREAD_TASK_GRAPH_RUNNER_H_

#include <memory>

#include "base/synchronization/condition_variable.h"
#include "base/threading/simple_thread.h"
#include "cc/raster/task_graph_runner.h"
#include "cc/raster/task_graph_work_queue.h"

namespace base {
class SimpleThread;
}

namespace cc {

// Runs TaskGraphs asynchronously using a single worker thread.
class CC_EXPORT SingleThreadTaskGraphRunner
    : public TaskGraphRunner,
      public base::DelegateSimpleThread::Delegate {
public:
    SingleThreadTaskGraphRunner();
    ~SingleThreadTaskGraphRunner() override;

    // Overridden from TaskGraphRunner:
    NamespaceToken GenerateNamespaceToken() override;
    void ScheduleTasks(NamespaceToken token, TaskGraph* graph) override;
    void WaitForTasksToFinishRunning(NamespaceToken token) override;
    void CollectCompletedTasks(NamespaceToken token,
        Task::Vector* completed_tasks) override;

    // Overridden from base::DelegateSimpleThread::Delegate:
    void Run() override;

    void Start(const std::string& thread_name,
        const base::SimpleThread::Options& thread_options);
    void Shutdown();

private:
    // Returns true if there was a task to run.
    bool RunTaskWithLockAcquired();

    std::unique_ptr<base::SimpleThread> thread_;

    // Lock to exclusively access all the following members that are used to
    // implement the TaskRunner interfaces.
    base::Lock lock_;

    // Stores the actual tasks to be run by this runner, sorted by priority.
    TaskGraphWorkQueue work_queue_;

    // Condition variable that is waited on by Run() until new tasks are ready to
    // run or shutdown starts.
    base::ConditionVariable has_ready_to_run_tasks_cv_;

    // Condition variable that is waited on by origin threads until a namespace
    // has finished running all associated tasks.
    base::ConditionVariable has_namespaces_with_finished_running_tasks_cv_;

    // Set during shutdown. Tells Run() to return when no more tasks are pending.
    bool shutdown_;
};

} // namespace cc

#endif // CC_RASTER_SINGLE_THREAD_TASK_GRAPH_RUNNER_H_
